Time constant Definition and 147 Threads

Homework Statement Find the time constantHomework Equations T=RC The Attempt at a Solution I understand the calculation fine. But I was wondering if the resistors are considered to be in parallel with each other even though the second resistor appears to be in parallel only with the...

Why is it generally assumed that time is and has been constant? When a star is described as being 150 million light/years away - how do we know that the time during those years passed at the same rate as time now. Couldn't time have been faster (or slower) in the past?

The exponentially weighted moving average is essentially a first order low pass filter: y(t)=(1-a)*y(t-1) + a*u(t) where y(t) is the present filter output, u(t) is the present filter input, y(t-1) is the filter output at the previous time and a is the smoothing factor or filter parameter...

1. A current in an RL circuit rises to one half of its maximum value in 7.0s. a) what is the inductive time constant for the circuit? b) if L= 0.8 H, what is the value of the resistance? 2. My book says the (time constant) = L/R 3. I've tried plugging into the above equation, but I...

I know that T = RC I've tried different combinations of R (not really sure what Req to take) but none of them worked. Any one can show me the right way ?

A defibrillator uses a capacitor to deliver a large current to a person needing heart stimulation. Assume that the capacitance used is 60microfarads and the resistor it discharges through is 220 ohms. the defibrillator is charged up to 5 kiloVolts and it is discharged through a patient for 1.0...

Homework Statement After how many time constants does the current in the figure below ( http://www.webassign.net/gianpse3/30-06.gif ) reach the following values? (a) within 67 percent of its maximum value (b) within 6.7 percent of its maximum value (c) within 0.67 percent of...

1. The switch in the figure has been closed for a very long time. A.) What is the charge on the capacitor? B.) The switch is opened at t = 0s. At what time has the charge on the capacitor decreased to 12% of its initial value? 2. Q=VC, tau= RC, etc. 3. A.) The capacitor...

Homework Statement If you were given an enclosed box, containing two 2000uF capacitors, which were either joined in series or in parallel, suggest, with a reason, how you would determine which way they were connected. Homework Equations C = C1 + C2 in parallel 1/C = 1/C1 + 1/C2 in...

Homework Statement Four identical capacitors are connected with a resistor in two different ways. When they are connected as in part a of the drawing, the time constant to charge up this circuit is 0.91 s. What is the time constant when they are connected with the same resistor as in part b...

Homework Statement A 11.0 uF capacitor in a heart defibrillator unit is charged fully by a 12000 V power supply. Each capacitor plate is connected to the chest of a patient by wires and flat "paddles," one on either side of the heart. The energy stored in the capacitor is delivered through...

Homework Statement A gust of wind hits a flagpole and starts it oscillating. After 10 s, the amplitude of its motion has decreased to 25% of its initial value. What is the value of the time constant? Homework Equations xmax(t) = Ae-t/\tau The Attempt at a Solution I know...

1. circuit consists of 10v supply, a switch, R1 (200ohm), R2 (100ohm) in series with a 1H inductance. with R3 (200ohm) across R1 and Inductance. I have to work out the time constants when switch is open and when closed. 2. when closed I have used 1 time constant = t = L/R, then 5 x L/R...

Homework Statement In my lab we where given a simple circuit and told to get some data of a capacitor charging and discharging. Thus I now have a graph of current vs time, we used semi-log paper for this so the graph would be a straight line. We are given the value of the resistor and...

Can anyone please tell me what the Time Constant of an RLC (Resistor, Inductor, Capacitor) circuit is?

Homework Statement I am trying to find the time constant of a thermometer that is taken from boiling water (100 deg C) and placed in ice water (0 deg C) Homework Equations See attached The Attempt at a Solution Using the equation in picture #1: I understand that I have to plot...

I'm curious: "A group of students needs to determine the time constant of a water tank. FIrst, the student establish an equilibrium level, with a known flow rate into the tank and both valves (solenoid and hand-operated) fully opened. One of the students reduces the input flow and the group...

Homework Statement sigh* Well, I have more than a week to do this lab, and usually I don't resort for help here, but on this lab there are so many things I am unsure of. So here's the setup of the lab: I have a one Farad capacitor, a DC power supply, a multimeter, a bunch of...

I made graphs of simple RC and RL circuits. We were told to mark off at 10% of the rise and 10% away from the max. This gives a delta. We were then supposed to use this information form the graph to calculate tau, and compare it with the theoretical value. I know how to calculate the...

Homework Statement Given y(t) = e^(-t) + e^(-t) How can we find the time constant from maths eqn (systems eqn to be exact)? Homework Equations The Attempt at a Solution t=-1 or 1?? always relate to e^(1)??

Homework Statement Three identical capacitors are connected with a resistor in two different ways. When they are connected as in part A of the drawing, the time constant to charge up this circuit is .34s. What is the time constant when they are connected with the same resistor as in part B...

Homework Statement A spring with spring constant 18.39 N/m hangs from the ceiling. A 452 g ball is attached to the spring and allowed to come to rest. It is then pulled down 4.62 cm and released. What is the time constant if the ball’s amplitude has decreased to 2.85 cm after 32 oscillations...

i understood every thing except at the last 30 seconds he says "after 5 time constants t=rc" current will be 0 i can't understand by what mathematical equation he got this number 5 ??

Hey, say I have a transfer function, G(s) = s/(6.25+s) How would I calculate the time constant for this transfer function? Also, if I wanted to sketch a bode plot for this transfer function, would I split it up into s* 1/(6.25+s) ? Thanks in advance.

Hi, I have a simple question: if I have a circuit with a capacitor, how do I calculate the voltage on the capacitor in function of time, I mean I know that tau(τ)=RC and there is the general formula X(t)=X(0)+[X(0)-X(∞)]-t/τ. So here comes my question should I consider the capacitor as the load...

Homework Statement A circuit with a battery that is in parallel with a resistor R1 followed series by a capacitor, which is in parallel with a resistor R2 Homework Equations Time constant = RC The Attempt at a Solution I do not know if it is correct to calculate RC with 1/Req =...

I am having a problem finding out how long it takes for a volatile liquid to evaporate when suddenly the pressure is reduced. For example - let's assume liquid butane at 8 bara is suddenly dropped to 1bara, the process of liquid turning to gas is not instantaneous so how long does it take...

1. The problem statement http://s685.photobucket.com/albums/vv212/dewdr0p714/?action=view&current=5circuittakehometest1.jpg 1) Determine the equivalent capacitance of the circuit 2) How many RC time constants are needed for the charge on the capacitors to reach 75% of their final...

Greetings I've been reading about these magnets such as these: http://www.lanl.gov/orgs/mpa/nhmfl/magnets.shtml Take a look at the pulse durations (it says in notes at the bottom "Total pulse length including decay" It's all nice but I don't understand one thing. How can they make...

Hihi, http://sales.hamamatsu.com/assets/applications/SSD/si_pd_circuit_kspd1043e06.pdf 5. high-sensor From the message there, I don't understand what is the meaning of time constant of resistor? Why does it say that the time response of the circuit depends on the time constant...

Hi, i am trying to design a circuit, where i am trying to light up an LED long enough based on my pulse signal. Here is what i am trying to do. a 10us pulse(every second) --->74HCT04 buffer---> (RC circuit)----> LED. since this is a 10us pulse, i want to make sure to light up the led for...

Homework Statement You see this trace on your oscilloscope for an RC circuit. The vertical scale is 5volt/square and the horizontal scale is 50ms/square. What is the time constant of the RC circuit? Homework Equations Vc(t) = Vo(e^(-t/RC) Vr(t) = -Vo * e^(-t/RC) t halftime = Tln(2) =...

where is this equation from? what does it equal?

I'm having trouble finding an equation for the time constant of an LRC circuit as a function of L, R and C. (In the same way that RC is time constant for an RC circuit) Does anyone know what the equation is? Thanks!

I was doing a lab about filters and the professor asked us, as an extra for the lab report, to explain why \tau = RC and why \tau = 63 \% of the total rise or decay. To be completely honest, I really don't know the answers for either question. I know it makes sense for \tau = RC if you just...

Given: slope of the graph of ln(temperature dimensionless) vs. time slope=-0.0416 -t/tau = ln(temperature dimensionless) I don't know where to put the slope into the equations? I know that the time constant is the tau. Also have -1/tau equation. I tried this...

if anyone could help me on this it would be much apreciated, thanks :smile: . Question: A capacitor was joined across a digital voltmeter and charged to a p.d. of 1V. the p.d. was then measured at 20s intervals and at t=30s a resistor (R=1.5 mega ohms (1500000ohms)) was connected across the...

I know that T = CR (time constant = capacitor rating times resistance) but I do not know how to calculate (theoretically) the time taken for the final ~36.8% of the capacitor to charge. The first language of the lecturer is not English. I, and others, can barely understand a word he says...

The problem is for a first-order instrument exposed to a step change of 100 units. If after 1.2 seconds the instrument indicated 80 units, estimate the instrument time constant. the problem I am having is chosen the correct formula for the time constant, any suggestions?

Hi everyone http://img36.imageshack.us/img36/5721/wave7xq.gif .[/URL] I'm in a little bit of a mess and need some help with this lab write up. There's no way of getting in touch with my TA and my professor didn't prove to be that great of a help when I went to see him yesterday. Anyways, we did...

In this lab, I'm supposed to find the average slope between a charging and discharging capacitor. For the slope of charging and for the slope discharging I used the basic formula y2-y1/x2-x1 choosing arbritary points on both lines. Charging slope = 4.6/-15, and discharging slope = 3.48/-57. Now...

OK, here is my frustration: I go to my lab, exchange equipment several times because some equipment is bad or wrong, do an experiment to show the time constant. First we charge the capacitor. Trial and error to find a good time increment. THEN, its time to discharge. AFTER 10 minutes of the...

I have a question that has confused me a little, A circuit is set up with a 10v battery,a 100 micro farad capacitor and a variable resistor. The capacitor is left to charge with the switch closed. After the switch is opened the variable resistor is adjusted to maintain a current of 100...

Can anyone tell me what formula I would use to find the time constant for a circuit that reaches 85% of its final value 1.86 seconds after the switch is closed.

Hi. How am I supposed to calculate the time constant for the enclosed circuit diagram. I know time constant t = 1/RC In this case do i take only one resistance or the combined value (series value) Assume any values. I only want to understand how it is to be done. PS: Sorry for the stupid...

capacitor --> time constant i'm blur with this q. a capacitor discharges through a resistor made of a length of wire. the time constant of the circuit is [tau1]. when the resistor is substituted with another wire made of the same metal but of twice the diameter and twice the length of the...

Hello there, I m very new to the forum n doesn't know that much manners of this forum.. I actually want to do a question... we did a practical in our university in which we determined the unknown resistance by using a neon flash bulb... I have to submit a report on that..i have to...